Sepsis is a significant healthcare issue due to its high frequency of occurrence and high mortality rate in hospitals. Sepsis is characterized by a whole-body inflammatory state, called a systemic inflammatory response syndrome (SIRS), and by the presence of a known or suspected infection. The immune system may cause this inflammatory response as a consequence of microbes in the blood, urine, lungs, skin, or other tissues, for example. One of the leading causes of sepsis is a bloodstream infection (BSI). BSI is most commonly diagnosed by a blood culture, in which a sample of blood is incubated with a medium in an atmosphere controlled to promote bacterial growth. Current automated blood culture systems can take 12-48 hours to detect the presence of infectious microorganisms in blood and can take up to 5 days to rule out the presence of any infectious microorganisms. It can take up to another 12-48 hours to identify the infectious microorganisms by sub-culturing the positive blood culture and performing identification and antimicrobial susceptibility tests. These results can be too late to alter the treatment course and result in the death of the patient. It would be advantageous if the time it takes to detect the presence of infectious microorganisms in the blood or other body fluid or tissue could be shortened to less than 24 hours, and more preferentially to less than 8 hours. Consequently, more time effective methods and apparatus for detecting the presence or absence of infectious microorganisms in a biological sample to determine, for example, if a patient has a BSI continue to be sought.